dilbert_
13th October 2009, 06:46 PM
There are many posts on GPS lag.
In some case there can be some extra problem but really GPS lag is to be expected because:
- it takes time to decode and compute GPS data from the RF signal;
- it takes time to transfer GPS data to the applications (for example a navigator);
- a typical GPS data refresh rate is 1 sec;
- a navigator is a computational intensive application and some delay in map refresh is to be expected.
All in all a lag between 1 and 2 sec would not be surprising and this kind of lag is quite noticeable (at 100 Km/h you move 28 m in a second).
If lag is not eliminable it can be compensated. A compensating application should:
1 - create a virtual serial port;
2 - wait for the GPS data;
3 - given position, speed and heading adjust position by moving it forward in heading direction by speed times a lag parameter;
4 - send the new GPS data to the virtual serial port;
5 - goto 2
On bends the compensation would not be perfect but navigators normally force the position to stay on the nearest road so they would mask this.
Now, an application like this is not very complex. I would develop it myself if I were a WM programmer and had the slighter idea of how create a virtual serial port...:o
In some case there can be some extra problem but really GPS lag is to be expected because:
- it takes time to decode and compute GPS data from the RF signal;
- it takes time to transfer GPS data to the applications (for example a navigator);
- a typical GPS data refresh rate is 1 sec;
- a navigator is a computational intensive application and some delay in map refresh is to be expected.
All in all a lag between 1 and 2 sec would not be surprising and this kind of lag is quite noticeable (at 100 Km/h you move 28 m in a second).
If lag is not eliminable it can be compensated. A compensating application should:
1 - create a virtual serial port;
2 - wait for the GPS data;
3 - given position, speed and heading adjust position by moving it forward in heading direction by speed times a lag parameter;
4 - send the new GPS data to the virtual serial port;
5 - goto 2
On bends the compensation would not be perfect but navigators normally force the position to stay on the nearest road so they would mask this.
Now, an application like this is not very complex. I would develop it myself if I were a WM programmer and had the slighter idea of how create a virtual serial port...:o